1. Field of the Invention
The present invention relates to an alkaline degreasing solution for degreasing the surface of a metal material such as iron, zinc, aluminum or an alloy thereof, or a non-metal material such as plastic or glass.
2. Description of the Background Art
In general, a degreasing treatment is carried out in order to remove fats and oils such as mineral oils and/or flora and fauna oils adhering to the surface of a target such as a metal material or a non-metal material, as a pretreatment for plating or coating, or simply for cleaning the surface. A cleaning solution which is employed for the degreasing treatment generally contains a builder mainly consisting of acid or alkali and a nonionic or anionic surface-active agent. As to waste water resulting from such a degreasing treatment, the COD value, oil concentration and the like are regulated, in order to maintain lake water or the like in good quality. In relation to waste water containing a surface-active agent, particularly a nonionic surface-active agent, however, it is well known that the surface-active agent can hardly be removed through neutralizing coagulation employing a general coagulant such as aluminum sulfate or iron chloride. In this case, therefore, the COD value is not reduced and the oil concentration cannot be sufficiently reduced either. Under the present circumstances, treated water which is passed through a neutralizing coagulation step is pretreated by dilution or the like, and thereafter subjected to an activated sludge treatment and an activated charcoal absorption treatment. Further, since a conventional degreasing solution which is reduced in degreasability due to aging is hard to treat, the same is generally diluted with water of 10 to 100 times in volume to be thereafter treated.
In relation to treatment of such waste water containing a surface-active agent, each of Japanese Patent Laying-Open No. 48-56579 (1973) and Japanese Patent Publication No. 60-251985 (1985) proposes a method of carrying out neutralizing coagulation by adding an organic substance having a phenolic hydroxyl group and an inorganic coagulant to the waste water.
Further, Japanese Patent Laying-Open No. 48-56579 discloses a method of treating waste water containing a surface-active agent with both of an organic substance having a phenolic hydroxyl group and an inorganic or organic coagulant.
On the other hand, Japanese Patent Publication No. 60-251985 discloses a method of adding a condensate obtained by a reaction of dihydroxydiphenylsulfone, lower aliphatic aldehyde and alkaline metal hydrogensulfite or alkaline metal sulfite to waste water containing a surface-active agent and thereafter adding a coagulant thereto.
In each of the aforementioned methods, however, it is necessary to add the treatment agent corresponding to the amount of the surface-active agent contained in the waste water, and hence the concentration of this surface-active agent must be measured before the addition of the treatment agent. If the treatment agent is excessively added, this treatment agent disadvantageously increases the COD value.
Further, it is necessary to sufficiently react the added treatment agent with the surface-active agent, and hence additional equipment and time are required for such reaction and the treatment steps are complicated.